[RFC v3 24/33] rust: drm/kms: Add RawPlaneState::atomic_helper_check()

[Lyude Paul <lyude@redhat.com>]

Add a binding for drm_atomic_helper_check_plane_state(). Since we want to
make sure that the user is passing in the new state for a Crtc instead of
an old state, we explicitly ask for a reference to a CrtcStateMutator.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 rust/kernel/drm/kms/crtc.rs  |  2 ++
 rust/kernel/drm/kms/plane.rs | 27 +++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index 99719c4e288e6..aaa208b35c3c1 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -593,6 +593,8 @@ pub trait AsRawCrtcState {
     }
 }
 
+pub(super) use private::AsRawCrtcState as AsRawCrtcStatePrivate;
+
 /// Common methods available on any type which implements [`AsRawCrtcState`].
 ///
 /// This is implemented internally by DRM, and provides many of the basic methods for working with
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index a30f7f8caaafb..63b453b7307fd 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -619,6 +619,33 @@ fn crtc<'a, 'b: 'a, D>(&'a self) -> Option<&'b OpaqueCrtc<D>>
         // SAFETY: This cast is guaranteed safe by `OpaqueCrtc`s invariants.
         NonNull::new(self.as_raw().crtc).map(|c| unsafe { OpaqueCrtc::from_raw(c.as_ptr()) })
     }
+
+    /// Run the atomic check helper for this plane and the given CRTC state.
+    fn atomic_helper_check<S, D>(
+        &mut self,
+        crtc_state: &CrtcStateMutator<'_, S>,
+        can_position: bool,
+        can_update_disabled: bool,
+    ) -> Result
+    where
+        D: KmsDriver,
+        S: FromRawCrtcState,
+        S::Crtc: ModesettableCrtc + ModeObject<Driver = D>,
+        Self::Plane: ModeObject<Driver = D>,
+    {
+        // SAFETY: We're passing the mutable reference from `self.as_raw_mut()` directly to DRM,
+        // which is safe.
+        to_result(unsafe {
+            bindings::drm_atomic_helper_check_plane_state(
+                self.as_raw_mut(),
+                crtc_state.as_raw(),
+                bindings::DRM_PLANE_NO_SCALING as _, // TODO: add parameters for scaling
+                bindings::DRM_PLANE_NO_SCALING as _,
+                can_position,
+                can_update_disabled,
+            )
+        })
+    }
 }
 impl<T: AsRawPlaneState + ?Sized> RawPlaneState for T {}
 
-- 
2.48.1